Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
  • B41J2/06—Ink jet characterised by the jet generation process generating single droplets or particles on demand by electric or magnetic field
  • B41J2002/061—Ejection by electric field of ink or of toner particles contained in ink

Definitions

• the present invention relates to a method of and apparatus for ejecting material from a liquid. More particularly, the method and apparatus employed may be generally of the type described in O-A-93-11866, PCT/GB95/01215 and WO-A-94-18011. In the methods described in these patent applications an agglomeration or concentration of particles is achieved at an ejection location and from the ejection location particles are then ejected onto a substrate, eg. for printing purposes. In the case of an array printer, plural cells may be arranged in one or more rows.
• an apparatus for ejecting material from a liquid comprises an ejection location having an electrode; means to apply an electrical potential to the ejection location electrode to form an electric field at the location; means for supplying liquid containing the particulate material to the ejection location; and a second electrode disposed adjacent to the ejection location, the voltage on the secondary electrode relative to the voltage on the ejection location electrode being controlled so as to reduce the sensitivity of the head to influence by external electric fields.
• the voltage on the secondary electrode may also be controlled to reduce the sensitivity of the head to variations in the distance between the ejection location and the substrate onto which the particles are ejected.
• the invention also includes a method of operating such apparatus to eject agglomerations of particles onto the substrate.
• the voltage on the secondary electrode relative to the voltage of the ejection location is controlled by a suitable electronic control circuit.
• the use of a secondary electrode is also particularly advantageous in an array system in which there are a plurality of cells in a row.
• the number of connections necessary to the electrodes at the ejection location and the secondary electrodes can each be reduced. For example, by connecting adjacent electrodes at the electrode location together in pairs and similarly for the secondary electrode the number of connections required for each set of electrodes is reduced by half.
• control of ejection and thus of printing can be achieved by selective application of voltages to the electrodes at the ejection location and the secondary electrodes in a "matrix addressing" mode since each ejection location electrode of a connected pair will be disposed opposite a secondary electrode of a different connected pair, ie. the opposing secondary electrodes will not be electrically connected.
• ejection voltages can be applied to the ejection location electrodes of a pair and ejection can be individually controlled from each of the respective cells by the application of different voltages on the opposing secondary electrodes. Further multiplexing can be achieved if desired.
• the secondary electrode is insulated and the ejection electrode is not, but in certain designs both may be non-insulated or both may be insulated or the ejection electrode insulated and the secondary electrode non-insulated.
• Figure 1 illustrates part of a printhead having a row of ejection cells and corresponding secondary electrodes;
• Figure 2 illustrates the arrangement of Figure 1 in side view
• Figure 3 illustrates, diagrammatically, an arrangement of the electrodes so as to allow addressing of individual ejection electrodes in pairs;
• Figure 4 illustrates, diagrammatically, how secondary electrodes can be used for a matrix addressing mode of operation
• Figure 5 is a partial perspective view of a portion of a further printhead incorporating ejection apparatus according to the present invention.
• Figure 6 is a view similar to Figure 5 showing further and alternative features of the ejection apparatus.
• Figure 7 is a partial sectional views through a cell of Figure 5.
• Figures 1 & 2 illustrate a printhead, diagrammatically, the printhead having plural cells 1 separated by insulating walls 2 and each containing an ejection electrode 3.
• agglomerations of particles carried by fluid in each of the cells can be ejected from the cells on application of a voltage to the respective electrodes 3 as indicated by the arrows in Figure l.
• Figure 2 shows a substrate 4 onto which agglomerations of particles, for example, for printing, are ejected from the cells 1.
• a secondary electrode 5 which has plural apertures 6 disposed opposite respective cells 3, is provided in front of the ejection cell.
• the electrode 5 is disposed on a first side of a support 7 and a further secondary electrode 8 is disposed on the other side.
• Charged agglomerations of particles emitted from the cell 1 pass through the electrodes 5 and 8 onto the earthed substrate 4.
• the voltages applied to the electrodes may be IkV on the ejection electrodes for ejection purposes, 500V on the secondary electrode 5 and OV on the further secondary electrode 8.
• the electrode support 7 may be provided by 150 micron thick glass slips chrome plated on both faces to provide the electrodes 5,8, and with the apertures 6 formed with 45 degree chamfered faces and having a width of 50 microns.
• the secondary electrode 8 may be separated from the outermost extremity of the ejection cell by a distance of 200 microns. It has been found generally that the closer the secondary electrode structure is to the ejection cell the greater the electric field in the region between them, but this also results in an increase in electrostatic pressure over the whole meniscus. The desired pressure distribution can be restored by increasing the potential on the secondary electrode 5.
• voltages on the electrodes may be as described in our British Patent Application 9601232.3, as described below.
• Figure 3 shows how the primary 3 and secondary 5 electrodes may be offset from one another and connected in pairs A,B,C,D,E,F etc. as referred to above.
• the number of connections required for each set of electrodes is reduced by half and by disposing the connected pairs of the secondary electrodes 5 offset with respect to the connected pairs of electrodes 3 at the ejection location, control of ejection and thus of printing can be achieved by selective application of voltages to the electrodes at the ejection location and the secondary electrodes in an "addressing" mode since each ejection location electrode 3 of a connected pair will be disposed opposite a secondary electrode of a different connected pair, ie. the opposing secondary electrodes will not be electrically connected.
• ejection voltages can be applied to the ejection location electrodes 3 of a pair and ejection can be individually controlled from each of the respective cells by the application of different voltages on the opposing secondary electrodes.
• the arrangement shown in Figure 4 is different again.
• This arrangement enables a matrix addressing scheme to be utilised to drive the apparatus.
• This addressing scheme is similar to that used, for example, in flat panel display technology and may be used to address N 2 ejection electrodes with 2N address lines.
• a 16 (4 2 ) element array is driven by 8 (2x4) address lines.
• the multiplex advantage is particularly significant with increasing numbers of electrodes, so that, for example, it would be possible to address a head with 256 (2 8 ) electrodes with 16 (2x8) address lines (8 primary and 8 secondary) .
• the detailed connection arrangements of the primary and secondary electrodes can be reversed of course if desired.
• Figure 5 illustrates part of an array-type printhead 1, the printhead comprising a body 2 of a dielectric material such as a synthetic plastics material or a ceramic.
• a series of grooves 3 are machined in the body 2, leaving interposing plate-like lands 4.
• the grooves 3 are each provided with a ink inlet and ink outlet (not shown, but indicated by arrows I & 0) disposed at opposite ends of the grooves 3 so that fluid ink carrying a material which is to be ejected (as described in our earlier applications) can be passed into the grooves and depleted fluid passed out.
• Each pair of adjacent grooves 3 define a cell 5, the plate-like land or separator 4 between the pairs of grooves 3 defining an ejection location for the material and having an ejection upstand 6,6'.
• two cells 5 are shown, the left-hand cell 5 having an ejection upstand 6 which is of generally triangular shape and the right-hand cell 5 having a truncated ejection upstand.
• Each of the cells 5 is separated by a cell separator 7 formed by one of the plate-like lands 4 and the corner of each separator 7 is shaped or chamfered as shown so as to provide a surface 8 to allow the ejection upstand to project outwardly of the cell beyond the exterior of the cell as defined by the chamfered surfaces 8.
• a truncated ejection upstand 6 1 is used in the end cell 5 to reduce end effects resulting from the electric fields which in turn result from voltages applied to ejection electrodes 9 provided as metallised surfaces on the faces of the plate-like lands 4 facing the ejection upstand 6,6' (ie. the inner faces of each cell separator) .
• the ejection electrodes 9 extend over the side faces of the lands 4 and the bottom surfaces 10 of the grooves 3. The precise extent of the ejection electrodes 9 will depend upon the particular design and purpose of the printer.
• Figure 6 illustrates two alternative forms for side covers of the printer, the first being a simple straight- edged cover 11 which closes the sides of the grooves 3 along the straight line as indicated in the top part of the figure.
• a second type of cover 12 is shown on the lower part of the figure, the cover still closing the grooves 3 but having a series of edge slots 13 which are aligned with the grooves.
• This type of cover construction may be used to enhance definition of the position of the fluid meniscus which is formed in use and the covers, of whatever form, can be used to provide surfaces onto which the ejection electrode and/or secondary or additional electrodes can be formed to enhance the ejection process.
• Figure 6 also illustrates an alternative form of the ejection electrode 9, which comprises an additional metallised surface on the face of the land 4 which supports the ejection upstand 6,6'. This may help with charge injection and may improve the forward component of the electric field.
• Figure 7 illustrates a partial sectional view through one side of the one of the cells 5 of Figure 5, with a secondary electrode 19 being shown located on the chamfered face 8 on the cell separator lands 4 and therefore disposed substantially alongside the ejection upstand.
• the secondary electrode may be formed, at least in part, on the face of the cell separator land 4 (and thus rearwardly of the ejection upstand) , with the ejection electrode also on the face, but separated therefrom.

Landscapes

• Particle Formation And Scattering Control In Inkjet Printers (AREA)
• Treating Waste Gases (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Seal Device For Vehicle (AREA)
• Electrostatic Spraying Apparatus (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1996
  • 1996-01-22 GB GBGB9601226.5A patent/GB9601226D0/en active Pending
• 1997
  • 1997-01-22 WO PCT/GB1997/000186 patent/WO1997027056A1/fr active IP Right Grant
  • 1997-01-22 DE DE69709318T patent/DE69709318T2/de not_active Expired - Lifetime
  • 1997-01-22 AT AT97901159T patent/ATE211072T1/de not_active IP Right Cessation
  • 1997-01-22 KR KR10-1998-0705604A patent/KR100483143B1/ko not_active IP Right Cessation
  • 1997-01-22 AU AU14504/97A patent/AU714514B2/en not_active Expired
  • 1997-01-22 RU RU98115850A patent/RU2141407C1/ru active
  • 1997-01-22 EP EP97901159A patent/EP0885126B1/fr not_active Expired - Lifetime
  • 1997-01-22 JP JP9526650A patent/JP2000503915A/ja active Pending
  • 1997-01-22 CA CA002241471A patent/CA2241471A1/fr not_active Abandoned
  • 1997-01-22 CN CNB971918236A patent/CN1177691C/zh not_active Expired - Lifetime
  • 1997-02-22 US US09/101,890 patent/US6247797B1/en not_active Expired - Lifetime
• 2006
  • 2006-08-16 JP JP2006222067A patent/JP2006347181A/ja active Pending

Non-Patent Citations (1)

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